In the processing of semiconductor devices, such as transistors, diodes, and integrated circuits, a plurality of such devices are typically fabricated simultaneously on a thin slice of semiconductor material, termed a substrate, wafer, or workpiece. In one example of a semiconductor processing step during manufacture of such semiconductor devices, the substrate or other workpiece is typically transported into a reaction chamber in which a thin film, or layer, of a material is deposited on an exposed surface of the substrate. Once the desired thickness of the layer of material has been deposited, the substrate may be further processed within the reaction chamber or transported out of the reaction chamber for further processing.
The substrate is typically transferred into the reaction chamber by way of a wafer handling mechanism. The wafer handling mechanism lifts the substrate from a position outside the reaction chamber and inserts the substrate into the reaction chamber through a valve formed in a wall of the reaction chamber. Once the substrate is transferred into the reaction chamber, the substrate is dropped onto a susceptor. After the substrate is received on the susceptor, the wafer handling mechanism is withdrawn from the reaction chamber and the valve is closed such that processing of the substrate can begin. In an embodiment, a susceptor ring is located adjacent to, and surrounds, the susceptor upon which the substrate is disposed during processing.
FIGS. 1-3 illustrates a known susceptor ring assembly 10 typically used in the Epsilon® tools produced by ASM America, Inc. of Phoenix, Ariz. The susceptor ring assembly 10 is a 2-piece structure that is disposed about, and adjacent to, a susceptor 12 that supports a substrate during processing. The susceptor ring assembly 10 is designed to absorb and retain radiant energy from heating source(s) during processing to reduce the amount of energy loss from the edge of the susceptor and substrate. The susceptor ring assembly 10 is also configured to receive and locate thermocouples at different locations about the susceptor 12, wherein the thermocouples are used to measure localized temperatures about the susceptor 12. The susceptor ring assembly 10 includes an upper ring 14 and a lower ring 16, wherein a gap 18 is formed between the upper and lower rings 14, 16. The thermocouples that measure the relative temperature adjacent to the susceptor at the leading edge, trailing edge, and a side edge are at least partially disposed within the gap 18. Each of these thermocouples is comprised of two wires formed of dissimilar metals that are fused at one end to form a thermocouple junction therebetween, an internal ceramic insulator that maintains a separation between the wires, and a sheath made of a non-conductive material able to withstand high temperatures and surround the ceramic insulator and wires.
Due to the fluctuation in temperatures within the reaction chamber as well as the high temperatures to which the two-piece susceptor ring is exposed, there are spaces, or gaps, that may form between the edges of the upper and lower rings 14, 16 of the susceptor ring assembly 10. These spaces often allow process gases to enter the gap 18 in which the thermocouples are located. The process gases can contact the outer surface of the thermocouples and cause deterioration of the thermocouple sheath. The deterioration of the sheath of the thermocouple may lead to a reduction in the accuracy of the temperature measured and the reduction of the lifetime of the thermocouple.
Because of the geometry of some of the thermocouples disposed within the two-piece susceptor ring assembly 10, it is typically necessary that the upper ring 14 is displaced or removed in order to install and remove some of these thermocouples. An access plate located adjacent to a wall of the reaction chamber typically must be removed before the upper ring 14 can be removed. Removing this access plate exposes the reaction chamber to air and moisture in the ambient air that can compromise the ability of the system to run some process applications. The geometry of the thermocouples and the two-piece susceptor ring also makes it difficult to install the thermocouples without scratching and damaging the outer sheath thereof.
A need therefore exists for a susceptor ring that can positively locate thermocouples about a susceptor while minimizing the amount of process gases and air to which the thermocouples are exposed. A need also exists for a susceptor ring that allows an operator to install thermocouples with minimal scratching and damage to the thermocouples.